In fossil fuel burners it is well known that the addition of water vapor enhances the combustion efficiency. Introduction of water vapor may be solely by positive pressure, U.S. Pat. No. 3,724,429; negative pressure (vacuum), U.S. Pat. No. 3,107,657; or both positive and negative pressure, U.S. Pat. No. 3,862,819. In this last-mentioned patent, the concept of water vapor introduced into a combustion chamber is applied to central heating units, such as oil heaters. This patent provides a fuel catalyzer which has a first conduit from the high pressure side of the fan associated with the oil burner to a position below a reservoir of water. A second conduit transports water vapor to the downstream side of the fan from a chamber above the reservoir.
The invention disclosed in U.S. Pat. No. 4,009,984 was directed to a system for regulating the metering of water vapor into the combustion area of a heating unit without altering the heating unit structurally. The invention employed only negative pressure (vacuum) and avoided fluctuation in the water level of a reservoir by utilizing a free floating platform which maintained a constant vapor chamber.
The invention comprised a vacuum-tight housing, a reservoir of water in the housing, and a constant vapor chamber disposed above the reservoir. A vacuum was created in the vapor chamber, which resulted in an airflow being drawn into the housing and through the reservoir. The airflow entrained metered amounts of highly vaporized water molecules which flowed into the vapor chamber and ultimately into the combustion chamber.
In the operation of that invention it was contemplated that for different-sized burners a valve would be sufficient to vary the amount of water vapor flowing into a combustion chamber. Practical experience has demonstrated that relying solely on the use of such a valve has not proven satisfactory, particularly because of the large variance in sizes of combustion chambers. Also it appeared that the use of a single flow passage for the introduction of air into the reservoirs was not always satisfactory, because of the non-uniformity of dispersion of air thorugh the reservoir and into the vacuum chamber.
The present invention is an improvement of the invention disclosed and claimed in U.S. Pat. No. 4,009,984. An apparatus and method are provided wherein the size of the vacuum chamber may be varied and uniform flow of air through the reservoir and into the vacuum chamber is achieved.
The invention comprises a tube adjustably secured to and depending from a free floating platform. The platform floats on a reservoir of water. The tube extends into the water and is characterized by a plurality of perforations. The perforations are immersed in the reservoir. Flow passages are formed externally of the tube whereby air is drawn through the flow passages, the water and ultimately into the vacuum chamber as a vapor stream.
In a preferred embodiment of the invention the tube is threaded into the platform and comprises an inner sleeve and an outer sleeve. A cover is secured to the upper edges of the sleeves. The sleeves define a flow passage. The inner sleeve below the water line is perforated. The portion of the cover lying between the inner and outer sleeves is apertured whereby when a vacuum is created in the vacuum chamber air flows in a uniform manner through the apertures, the water in the reservoir, the perforations of the inner sleeve and into the vacuum chamber.